This invention relates in general to the field of electronic devices. More specifically, this invention relates to an apparatus and method for restricting process fluid flow during semiconductor processing.
Semiconductor fabrication typically includes depositing material onto a semiconductor substrate wafer and etching material from the substrate. Often these processes take place within a process chamber containing one or more wafers and a deposition apparatus referred to as a showerhead. The showerhead acts to direct process fluid to the semiconductor substrate wafer. The showerhead typically includes an inlet conduit connected to a process fluid source outside of the process chamber and a showerhead plate with a number of holes extending therethrough to direct process fluid exiting the showerhead to the semiconductor substrate wafer. Showerheads are also used in both material deposition and etching processes to direct deposition and etching fluid to the semiconductor substrate wafer.
Problematic edge effects often result from uneven deposition and etch across the radius of a semiconductor substrate wafer. These problems often result when the characteristics of a plasma field or the flow of process fluid varies between the center of the wafer and the edge of the wafer. Such nonuniform deposition and etch often results in a semiconductor substrate wafer with disparate electrical properties across its radius. Because of this disparity portions of the wafer are often not usable for their intended function. In the case of circular wafers, inadequate deposition and etching of material adjacent to the outer edge of the wafer often renders devices formed adjacent to the outer edge of the wafer defective. As wafer diameter increases from six inches-to eight inches-to twelve inches, the number of devices formed adjacent to the outer edge increases significantly. Therefore, edge defects for a twelve inch wafer result in a greater number of unusable devices as compared with a six inch wafer.
One past solution for controlling deposition and etch across the radius of a wafer was to alter the geometry of holes extending through a showerhead plate. This technique allows process fluid to be directed toward selected areas of the substrate wafer. Simply, to increase process fluid flow to selected areas, more or larger holes are formed in the showerhead plate opposite those areas. However, this solution suffers from a number of drawbacks. First, a specialized showerhead plate is typically formed for a particular process and is often not useful for other processes. Second, experimentation with a specialized showerhead plate is time consuming and expensive. A complete processing run is often required to evaluate the effectiveness of a particular geometry of holes in a showerhead plate. This consumes valuable resources and processing time. Third, the use of specialized showerhead plates for each deposition and etch process step can be costly, often requiring multiple showerhead assemblies to perform multiple processing steps and replacing showerhead assemblies to accomplish process changes.
Therefore, a need has arisen for an apparatus that can selectively control deposition and etching on the outer edge of a semiconductor substrate wafer.
A further need has arisen for an apparatus that can selectively control the deposition and etching of material across the radius of a semiconductor substrate wafer.
A further need has arisen for an apparatus that is operable to selectively vary deposition and etch edge effects in a plurality of processes.
In accordance with teachings of the present invention, an apparatus and method are described which substantially eliminates or reduces disadvantages and problems associated with prior apparatuses and methods used to deposit and etch materials during semiconductor fabrication. The apparatus includes a process chamber and a blocking assembly disposed within the process chamber. The blocking assembly may be selectively positioned in an active or neutral position. When positioned in the active position, the blocking assembly restricts process fluid flow directed toward a substrate wafer from a showerhead assembly disposed in the process chamber. When positioned in the neutral position the blocking assembly does not restrict the flow of process fluid between the showerhead assembly and the substrate wafer.
In one aspect of the present invention a semiconductor processing apparatus is disclosed. The semiconductor processing apparatus includes a process chamber and at least one substrate support disposed within the process chamber operable to support a substrate wafer. The semiconductor processing apparatus also includes at least one showerhead assembly disposed within the process chamber that faces the substrate support and has a showerhead plate. The showerhead plate has a plurality of passageways extending therethrough for directing a process fluid toward a substrate wafer disposed on the substrate support. A blocking assembly is disposed within the process chamber. The blocking assembly has an active position between the showerhead assembly and the substrate support to restrict the flow of process fluid between the showerhead assembly and the substrate support. The blocking assembly also has a neutral position that does not restrict the flow of process fluid between the showerhead and the substrate support. More specifically, the blocking assembly includes at least one blocking disk that has an outer diameter smaller than the outer diameter of the substrate wafer. Also, the at least one blocking disk is selectively movable between the active position and the neutral position.
In another aspect of the present invention a process fluid blocking assembly for controlling the flow of a process fluid in a semiconductor processing apparatus is disclosed. The process fluid blocking assembly includes a rotator selectively rotatable and at least one blocking disk having a substantially circular configuration. The blocking assembly also includes a linkage having a first end and a second end. The first end of the linkage is coupled to the rotator and the second end is coupled to the at least one blocking disk such that the blocking disk rotates as the rotator rotates. More specifically, the process fluid blocking assembly includes a plurality of blocking disks having multiple disk sizes where the plurality of blocking disks is operable to releasably couple to the linkage.
In another aspect of the present invention, a method for fabricating a semiconductor device on a substrate wafer disposed in a semiconductor fabrication apparatus is disclosed. The method includes supplying process fluid to a showerhead assembly positioned opposite the substrate wafer. The method also includes selectively positioning a blocking assembly between the showerhead assembly and the substrate wafer to restrict the flow of process fluid from the showerhead to the substrate wafer. This selective positioning of the blocking assembly affects the fabrication of the semiconductor device.
The present invention provides a number of important technical advantages. One technical advantage is having at least one blocking disk that has an outer diameter smaller than the outer diameter of the substrate wafer. This allows the deposition apparatus to selectively control deposition on the outer edge of the substrate wafer.
Another technical advantage of the present invention is having a blocking assembly with an active position and a neutral position. This allows the deposition apparatus to selectively control the deposition and etching of material across the radius of a substrate wafer.
Another technical advantage of the present invention is having a plurality of blocking disks having multiple disk sizes, operable to releasably couple to the linkage. This allows the blocking assembly to selectively vary deposition and etch edge effects in a plurality of processes.